In an instance where sound produced by striking a head of an acoustic drum, such as a snare drum, is sustained too long, the sound of the acoustic drum is mixed with sound produced by other percussion instruments and accordingly becomes difficult to listen to. For permitting the sound produced by the acoustic drum to easily listen to or for suppressing sound of unnecessary components, the head is provided with extraneous matter for vibration damping (muting). For instance, a mute ring is placed on the head or a tape or gel for muting is attached to the head. Further, felt is put on a back surface of the head from inside of the shell or on a front surface of the head from outside of the shell. As disclosed in the following Patent Literature 1, there is known a configuration in which a casing has a support portion for supporting a mute ring or the like.